Method of recovering metals and producing a secondary slag from base metal smelter slag

A method of recovering metals and producing a secondary slag from base metal smelter slag produced by a copper or nickel smelter, said smelter slag comprising iron silicate and other metallic compounds and elements including (by weight):

• from about 15% to about 40% SiO.sub.2
• from about 1% to about 8% Al.sub.2 O.sub.3[s ]
• from about 35% to about 60% Fe.sub.2 O.sub.3
• from about 2% to about 20% CaO
• from about 1% to about 3% MgO
• from about 0.2% to about 1% Cu (when from a copper smelter)
• from about 0.1% to about 1% Ni (when from a nickel smelter)
• from about 0.1% to about 0.3% Co
• from about 0.2% to about 2% S
• said method comprising:
• mixing the smelter slag with at least one reducing agent selected from the group consisting of carbon and aluminum, said carbon being from about 1% to about 10% by weight of the slag and said aluminum being from about 5 to about 30% by weight of the slag, and with from zero to about 60% calcium oxide by weight of the slag, and heating the mixture above a eutectic melting point thereof to reduce the iron silicate to ferrosilicon containing copper, nickel or cobalt which was in the smelter slag and thereby also produce a secondary slag comprising at least one compound selected from the group consisting of calcium silicate, calcium aluminate and calcium iron aluminum silicate, and separating the ferrosilicon from the secondary slag.